The present invention relates to an image forming apparatus such as a copying machine of an electrophotographic type, a printer and a facsimile machine, and in particular, to a process cartridge which is capable of being mounted on or dismounted from an image forming apparatus having therein a heating and fixing unit.
A process cartridge is structured as a unit which contains in its housing an image carrier (a photoreceptor drum), a developing unit and other processing members. When developing agents in a developing unit and an image carrier are deteriorated to lower image quality, the process cartridge is removed from the main body of an image forming apparatus to be replaced with a new process cartridge.
Some image forming apparatuses in which the process cartridge of this kind is loaded employ toner of a heat-fixing type as developing agents and a fixing-heat roller in a heat-fixing device. In the heat-fixing device, a transfer material onto which an unfixed developed image has been transferred is nipped between the fixing-heat roller and a pressure roller to be conveyed, and thereby the unfixed developed image is heated and fused to be transferred onto the transfer material. A conventional heat-fixing device has been provided on the part of the main body of an image forming apparatus.
The fixing device described in Japanese TOKKAIHEI No. 2-29767 is one wherein a fixing cartridge including a heat roller is structured to be capable of being mounted on and dismounted from the main body of an apparatus, and a slidable power-supplying member which slides on a power-receiving member for the heat roller of the fixing cartridge is provided on the part of the main body of an apparatus.
With regard to the process cartridge and the image forming apparatus in Japanese TOKKAIHEI No. 2-19858, a fixing film which moves solidly with a transfer material and a roller around which the fixing film is wound are housed in the process cartridge which houses therein an image carrier and other process units and is capable of being mounted on and dismounted from the image forming apparatus.
The image forming apparatus in Japanese TOKKAIHEI No. 2-149859 is an image forming apparatus wherein a cleaner for fixing is provided to be capable of being mounted on and dismounted from a process cartridge having therein a drum-shaped photoreceptor, a developing unit and a cleaning device.
The printer in Japanese TOKKAIHEI No. 2-272462 is one wherein a unit in which a photoreceptor drum, a charging device, a developing device, a transfer device, a toner cartridge, a toner collecting device, a waste toner container and a cleaning pad for a fixing roller are integrally formed is capable of being mounted on and dismounted from the main body of the printer.
The image recording apparatus in Japanese TOKKAIHEI No. 4-50952 is one wherein a part of a heating means of a heat-fixing device and a photoreceptor cleaning device are united to be one body which is capable of being mounted on and dismounted from the main body of the image recording apparatus, and heat energy of the heating means is impressed on collected toner.
The electrophotographic apparatus in Japanese TOKKAIHEI No. 8-123295 is one wherein a fixing device representing a heating body is provided in the main body of the electrophotographic apparatus, a photoreceptor belt is provided on a process unit, and an infrared ray reflecting member is mounted on an enclosure of the process unit that faces the fixing device.
(1) In the prior art, a process cartridge and a fixing-heat roller are structured to be separate from each other, and the fixing-heat roller is provided on the part of the main body of an image forming apparatus. Even in the case where the process cartridge and the fixing-heat roller are the same in terms of life, the process cartridge has been capable of being mounted on and dismounted from the main body of the apparatus. On the occasion of maintenance of the apparatus, it has been necessary to remove the process cartridge and a fixing-heat roller supporting member separately and to replace them or to clean them, requiring much manhours for maintenance.
(2) Since a photoreceptor drum and the fixing-heat roller are provided respectively on different units, adjustment has been needed for maintaining their positional relation (parallelism).
(3) Since a conveyance unit having a fixing-pressure roller which is supported rotatably on the apparatus main body is made to hit a part of a process cartridge, the position where the process cartridge is supported is important.
(4) In the event of maintenance, when parts requiring no replacement are provided on a process unit, the process unit proves to be expensive when the unit is replaced.
(5) Even in the case of cleaning of the process unit instead of replacing thereof, cleaning is easy if no parts are arranged around the fixing-heat roller.